1. Field of the Invention
This disclosure pertains to aerial deck and work platforms which are mounted on single or multi-section telescopic or articulated booms to position the platform at a selected elevation and position relative to a chassis or other support structure. More specifically, the disclosure pertains to apparatus which is more efficiently able to position large sized work platforms with telescopic booms although articulated booms can also be used instead.
2. Description of the Related Art
Boom mounted work platforms are typically of rectangular configuration and, frequently, it is desirable to position the long side of the rectangular platform in close proximity to a vertical wall or to the vertical edge of a horizontal deck. Ideally, this should be easily accomplished without having to reposition an entire mobile vehicle on which the boom and work platform is supported.
One prior art example of a telescopic boom having a large work platform non-rotatably supported thereon is the Manitou 150 TP which has a relatively short platform supported slide out deck which overlaps the main deck of the platform when the slide out deck is retracted.
A second example of known prior art is the Nagano NUZ090D device in which a rectangular work platform of about 7 feet by 10.5 feet is mounted at the upper end of a telescopic boom for rotation about a vertical axis relative to the boom. Although the platform can be rotated, it cannot be laterally translated relative to the boom. The long sides of the work platform in this device are ordinarily aligned parallel to the longitudinal axis of the mobile support on which the boom is mounted.
Rotation of a large work platform relative to the boom creates very large torsional forces on the supporting boom which require substantial additional structural strength. The prior art platforms have therefore been limited in size by either using a rotatable platform while ensuring that the vertical axis of rotation of the platform is not located too far from a centered position over a mobile support structure or by merely precluding rotation of the platform relative to the boom and using a small slidable deck instead.
A more efficient arrangement is desired which is capable of longitudinal and rotational positioning for large workloads and in which the work platform and supporting boom may be closely positioned and stowed over the support structure, usually a mobile wheeled vehicle, during movement to different work locations.